Nuclear magnetic resonance (NMR) spectrometers were used to acquire data on many different elements long before the use of the magnetic resonance systems for imaging purposes. The "spins" of different elements precess at different frequencies which are known as the Larmor frequencies. Accordingly, even before magnetic resonance imaging (MRI) either extremely broad band matching and decoupling networks that function over the wide frequency bands necessary for getting data from the moments of different elements or different matching and decoupling networks for each of the individual moments of the different elements on which data is to be taken were used. Having to change the matching and decoupling networks during examinations, of course, involves extra equipment with the added expenses as well as the added time for either actually physically changing or switching between equipment. In either case, the extra equipment adds to cost of the system.
Presently MRI and magnetic resonance spectroscopy systems are used to acquire morphylogical and physiological data from such elements as phosphorous, sodium and hydrogen, among others. In magnetic fields of 1.9 Tesla the Larmor frequency for phosphorous (P) is 32 MHz. The Larmor frequency for sodium (NA) is 21 MHz and the Larmor frequency for hydrogen (H) is 81 MHz. Therefore, MR systems require tailored matching and decoupling networks for those elements or broad band matching and decoupling networks capable of being used when acquiring data on diverse elements. The broad band matching and decoupling network is a preferable solution but providing such networks has proven extremely difficult and/or expensive.
Among the difficulties encountered when attempting to use broad band matching and decoupling networks is due to the fact that in many MR systems both the receiving and transmitting operations use the same radio frequency RF coil. Therefore, the switching between the receiving mode and the transmitting mode must be accomplished in short time spans. Any frequency dependent components (capacitors, inductors) could be adversely effected by short switching times--i.e. transients are formed. Accordingly the matching and decoupling network ideally should have frequency independent components.